<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <link rel="stylesheet" href="./css.css">
</head>
<body>
    123
    <div id="box">123</div>
    <input type="button" id="btn">
</body>
<script>
    document.onload = function(){
        console.log("文档加载完成")
    }

    window.onload = function(){
        console.log("浏览器加载完成")
    }

    btn.onkeydown = function(){
        console.log("键盘按下")
    }
</script>
</html>